Simson: "DC, why are you doing siyahs? You can easily steam in that statics! Even steeper angles and tighter curves are possible with a natural stave."
I don't know why HE'S doing siyahs, but when I did them it was either to stretch my wood budget by using something too short otherwise, OR, just to see if I could do it that way. I did recurves THIS way, let's see if I can do it this OTHER way.
PatM is all over this. A triangle cross section is about 88% as stiff and strong as a square cross section the same biggest dimension, but something like 40% lighter.
I even make Mollie levers either a pretty skinny trapezoid or Gothic arch cross section.